Darkness time in orbit charts! Or how to stop putting so many batteries on your ships

[Savvy]

I became obsessed with planning every bit of a mission using calculators, charts or anything to stop putting thing at random. But I would always put so many batteries... So I made those charts to find out how much time your ship will spend in darkness for every body in the Kerbol system and it includes the synchronous orbit as well as the moons altitudes for reference, and it has been calculated for circular orbit.

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I made those charts using a MATLAB script, I wanted to get my hand around it and it turned out pretty well. Hope these we'll be useful for ya!

Edited August 6, 2014 by Savvy

[K77LostNSpace]

Very good information. Thanks for all the work you put into these charts.

Quick question reading the information. the time is in seconds?

[7499275]

Very good information. Thanks for all the work you put into these charts.

Quick question reading the information. the time is in seconds?

Are you aware on how to read a graph? The Y axis states "darkness time (s)"

If you are unaware. The S referes to seconds, M would be minutes, H hours, and so on.

M could also refer to months but use best judgement base on the context of the graph for that.

[Savvy]

Very good information. Thanks for all the work you put into these charts.

Quick question reading the information. the time is in seconds?

Thanks, it took me quite a while to do. Yes the time is in second, as you can see on Y axis label.

[K77LostNSpace]

I guess some people have never heard of the phrase the dumb question is the one not asked.

But to answer 7499275, no I'm not that familiar with graphs, I rarely use them in my daily life.

[7499275]

I guess some people have never heard of the phrase the dumb question is the one not asked.

But to answer 7499275, no I'm not that familiar with graphs, I rarely use them in my daily life.

Sorry if I came off as... Harsh, didn't mean to in anyway if it seamed it!

[Pecan]

Excellent information. Thank you.

[Savvy]

Excellent information. Thank you.

Glad I could help!

[Potato Shadow]

Does the inclination matter ? Or as long as it's a circular orbit the graph applies ? (Pretty sure it doesn't but just making sure.)

[hab136]

Neat!

I note that the moon charts don't seem to include the shadow from the main planet.

For example the chart for Kerbin says about 4500 s of darkness for something orbiting Kerbin at the same height as Minmus. So obviously anything orbiting Minmus will be subjected to about 4500 s of darkness when Minmus is in Kerbin's shadow.. yet the chart for Minmus starts around 1000 s.

If you want 100% coverage, you'll have to check both the moon's numbers and its parent planet's numbers. You can't just look at the parent planet's numbers, though, since some of the moons have longer darkness times - for example Eve has a blackout of about 2700 s for something in Gilly's orbit, but Gilly goes up to about 3300 s.

A combined chart (darkness time from moon's shadow + darkness time from parent planet, taking into account moon's height + height above moon) would be interesting. Maybe two lines on the moon charts - one just with the moon's shadow, one with moon + parent planet's shadow?

Does the inclination matter ? Or as long as it's a circular orbit the graph applies ? (Pretty sure it doesn't but just making sure.)

As long as your orbit is circular, your inclination doesn't matter, since these are worst-case numbers (half of orbit in shadow, half in sunlight).

Depending on your inclination you can have less darkness - for example if you're in a polar orbit, it's possible to be 100% in sunlight during part of the year. However the planet will eventually turn so that you're halfway in the sun and halfway in shadow, so these numbers are still relevant as worst-case darkness.

If you had a non-circular, highly elliptical orbit (like http://en.wikipedia.org/wiki/Molniya_orbit) then you could manage to put yourself in darkness for longer (for part of the year; the same orbit during the opposite part of the year would be mostly sunlight).

[Potato Shadow]

-snip-

As long as your orbit is circular, your inclination doesn't matter, since these are worst-case numbers (half of orbit in shadow, half in sunlight).

Depending on your inclination you can have less darkness - for example if you're in a polar orbit, it's possible to be 100% in sunlight during part of the year. However the planet will eventually turn so that you're halfway in the sun and halfway in shadow, so these numbers are still relevant as worst-case darkness.

If you had a non-circular, highly elliptical orbit (like http://en.wikipedia.org/wiki/Molniya_orbit) then you could manage to put yourself in darkness for longer (for part of the year; the same orbit during the opposite part of the year would be mostly sunlight).

Thanks for clarifying

[Savvy]

If you want 100% coverage, you'll have to check both the moon's numbers and its parent planet's numbers. You can't just look at the parent planet's numbers, though, since some of the moons have longer darkness times - for example Eve has a blackout of about 2700 s for something in Gilly's orbit, but Gilly goes up to about 3300 s.

I don't understand: why would the time in orbit around a moon will be different than the time we can find on the parent's body? I tried looking for a different formula but can't find any.

[qazsedcft]

What formula did you use? This doesn't seem right to me because as you get further the shadow of the planet becomes narrower and covers a smaller portion of the orbit.

[Kasuha]

It would be nice to add a horizontal line to each graph for each moon, showing darkness time potentially produced by the planet. E.g. for Mun there would be a line at 2200 (+/-) seconds showing that not only you can get ocluded by the Mun, but by Kerbin as well - as in the worst case these two can add up. My Laythe probe once crashed due to that as Jool eclipse started right after it left Laythe shadow.

[Savvy]

What formula did you use? This doesn't seem right to me because as you get further the shadow of the planet becomes narrower and covers a smaller portion of the orbit.

Look at this :

The further you go the longer the black part will be.

Edited August 7, 2014 by Savvy

[Grover]

Neat!

I note that the moon charts don't seem to include the shadow from the main planet.

For example the chart for Kerbin says about 4500 s of darkness for something orbiting Kerbin at the same height as Minmus. So obviously anything orbiting Minmus will be subjected to about 4500 s of darkness when Minmus is in Kerbin's shadow.. yet the chart for Minmus starts around 1000 s.

If you want 100% coverage, you'll have to check both the moon's numbers and its parent planet's numbers. You can't just look at the parent planet's numbers, though, since some of the moons have longer darkness times - for example Eve has a blackout of about 2700 s for something in Gilly's orbit, but Gilly goes up to about 3300 s.

A combined chart (darkness time from moon's shadow + darkness time from parent planet, taking into account moon's height + height above moon) would be interesting. Maybe two lines on the moon charts - one just with the moon's shadow, one with moon + parent planet's shadow?

As long as your orbit is circular, your inclination doesn't matter, since these are worst-case numbers (half of orbit in shadow, half in sunlight).

Depending on your inclination you can have less darkness - for example if you're in a polar orbit, it's possible to be 100% in sunlight during part of the year. However the planet will eventually turn so that you're halfway in the sun and halfway in shadow, so these numbers are still relevant as worst-case darkness.

If you had a non-circular, highly elliptical orbit (like http://en.wikipedia.org/wiki/Molniya_orbit) then you could manage to put yourself in darkness for longer (for part of the year; the same orbit during the opposite part of the year would be mostly sunlight).

That is not true, as a circular polar orbit with its plane aligned with the prograde vector of the planet would be in consant daylight: the inclination matters very much and is as important as the orbital radius

[Savvy]

It would be nice to add a horizontal line to each graph for each moon, showing darkness time potentially produced by the planet. E.g. for Mun there would be a line at 2200 (+/-) seconds showing that not only you can get ocluded by the Mun, but by Kerbin as well - as in the worst case these two can add up. My Laythe probe once crashed due to that as Jool eclipse started right after it left Laythe shadow.

Wouldn't referring to the parent planet be sufficient ? Because sometime the scale on the Y axis for a moon will not be enough to show that horizontal line. But that's a good idea I'll look into it.

[zarakon]

What formula did you use? This doesn't seem right to me because as you get further the shadow of the planet becomes narrower and covers a smaller portion of the orbit.

The shadow covers a smaller percentage of the orbit as you get farther out, but the whole orbit is also larger and takes longer.

For a circular orbit, the section that's in shadow actually gets slightly shorter in terms of distance, as the arc becomes straighter. However, the slower orbital speed to traverse that section more than makes up for that

[Kasuha]

I believe the shadow becomes actually the wider the higher the orbit - because the shadow is measured relative to Sun center and the planet's circumference. But I doubt it makes any big difference anywhere.

[qazsedcft]

Look at this : http://wiki.kerbalspaceprogram.com/w/images/0/01/Orbit_Darkness.jpeg

The further you go the longer the black part will be.

Well, I'm not sure how realistic the light model in KSP is, but in real life that's incorrect because the shadow should be a cone not a cylinder. The cone (or triangle in your 2D drawing) should have the same proportions as the cone extending from the Sun to your planet, so it approaches a cilinder at infinity (or if the sun is modeled as an unrealistic point light).

[qazsedcft]

I believe the shadow becomes actually the wider the higher the orbit - because the shadow is measured relative to Sun center and the planet's circumference. But I doubt it makes any big difference anywhere.

That's the penumbra, not the shadow itself (umbra). See http://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra

[Savvy]

Well, I'm not sure how realistic the light model in KSP is, but in real life that's incorrect because the shadow should be a cone not a cylinder. The cone (or triangle in your 2D drawing) should have the same proportions as the cone extending from the Sun to your planet, so it approaches a cilinder at infinity (or if the sun is modeled as an unrealistic point light).

See this : http://wiki.kerbalspaceprogram.com/wiki/Orbit_darkness_time#Limitations

As far as the SOI is this shouldn't make a big difference, the sun's rays are parallel and it's sufficient to work out how many batteries will be needed.

[Aragosnat]

Well, I'm not sure how realistic the light model in KSP is, but in real life that's incorrect because the shadow should be a cone not a cylinder. The cone (or triangle in your 2D drawing) should have the same proportions as the cone extending from the Sun to your planet, so it approaches a cilinder at infinity (or if the sun is modeled as an unrealistic point light).

Don't think it is close to realistic. As at times I should be getting light to the panels. But, don't. Hope I'm wrong about it too.

[AlexisBV]

As at times I should be getting light to the panels. But, don't.

Funny, often I get light on the panels when I shouldn't. Mountains/terrain above sea level appear to be transparent as far as solar panels are concerned.

[qazsedcft]

@Savvy: OK, that's what I suspected. Makes sense now.